The present invention relates generally to tires and in particular to multi-chambered tires. More particularly this invention relates to an inner tubeless pneumatic shield or inner tire for race tires. This invention provides an improved shield of the type described in U.S. Pat. No. 4,995,438.
Race tires may have an inner tire, otherwise known as a shield, which is mounted on the ledge of the bead seating portion of a rim and which is axially inward of the bead portions of the outer tire. The inner tire has a crown portion, which when mounted, is spaced from the inner surface of the crown or ground engaging portion of the outer tire, and a pair of sidewalls which extend from the axial edges of the crown portion to a bead portion. Each, bead portion of the inner tire has a bead core (an annular tensile member) therein. In other words, the inner tire or shield when mounted upon a tire and rim assembly acts as a tire within a tire which helps in stabilizing a vehicle after an outer tire failure. This divides the tire assembly into outer and inner chambers, the outer chamber being the space between the radially outer surface of the inner tire and the radially inner surface of the outer tire while the inner chamber is formed by the inner surface of the inner tire and the rim of the wheel. Typically air is retained within the inner chamber by an air container, such as a tube. The chambers can then be inflated by a dual inflation valve in which air passes through grooves in the radially inner end and axially outer end of the bead portions, such as illustrated in U.S. Pat. No. 3,476,168 to HUBER, et al.
In tires in general, and race tires in particular, it is important to keep the weight of the tire and rim assembly to a minimum in order to optimize fuel efficiency and to decrease the amount of rotating mass to provide for more rapid acceleration/deceleration. A tire and wheel assembly as described above may weigh for example from about 60 lbs. to about 70 lbs. for a 28.0.times.10.0-15 size tire and a 9.5.times.15" rim. The air container or inner tube of such an assembly may weigh about 5 lbs. Therefore, if the inner tube could be eliminated, this would result in the tire and wheel assembly being reduced in weight from about 7% to a little more than 8%, which would result in about a 20 lb. reduction in total rotating mass.
The elimination of the air container from the tire and wheel assembly also would eliminate the problem associated with a failure of the air container. If the air container fails, air is then able to pass from the air container to the outer chamber which will result in an equalization of air pressure in both chambers.
The prior art inner shields as disclosed above have conventional automotive type bead wires which are large, stiff, and easily deformed under severe bending. The bent bead wires in most cases prevented the inner shield from properly sealing against the rim flange, thus rendering the shield useless.
Shields with protrusions as disclosed in U.S. Pat. No. 4,995,435 in some cases would not seat properly upon a rim because the shield would get stuck on the outer surface of the bead portion radially inward of the protrusion.
It is important that the inner shield properly and automatically seals against the rim flange because the outer tire prevents access to the inner shield during inflation of the assembly. A shield according to the present invention can be manufactured which is more easily assembled with a consistently high reliability of proper bead seating.